Surface Currents

1
Surface Currents

• Flow of water in the uppermost layer of the ocean
  driven by wind

2
Wind and Currents

• Strongly affected by the Coriolis Effect
• The eastward rotation of earth on its axis
  deflecting the moving water or air away from its
  initial course
• http//www.classzone.com/books/earth_science/terc/
  content/visualizations/es1904/es1904page01.cfm

3
Which direction??
4
Wind Patterns

• Driven by solar heating
• Warm at equator
• Cold at poles
• Molecules move from warm to cold
• Also affected by moisture (density)
• As warm air rises at equator, new air rushes in
  to replace it ? wind

5
Formation of Trade Winds
6
There are 6 atmospheric circulation cells
7

• Winds are bent by Coriolis Effect (45o)
• http//www.mhhe.com/biosci/genbio/tlw3/eBridge/Chp
  29/animations/ch29/global_wind_circulation.swf

8
Surface Currents

• Major wind fields create sea surface currents
• Uppermost layer of surface water moves at angle
  45o due to Coriolis effect

9
Ocean Surface Currents

• Trade winds move toward the equator, equatorial
  ocean current produced move parallel to equator

10

• Due to Coriolis effect, the surface currents
  combine into circular systems ? gyres
• Northern Hemisphere clockwise
• Southern Hemisphere - counterclockwise

11
(No Transcript)
12
Ekman transport

• Top layer of water pushes on water below it but
  bends slightly to right
• Processes continues down through water column
  creating Ekman spiral

13
Effects of Ekman Transport

• Effect of wind decreases w/ depth
• Affects top 100 m (Ekman layer)
• Overall Ekman layer moves at 90o from wind
  direction

14
Climate Regulation

• Water transports heat
• Ocean Currents act like global thermostat
• Solar heat from Equator carried to higher
  latitudes warms poles
• Cold water currents cool tropics

15
Currents Affect Organisms

• Surface temp higher on western side of ocean
• Currents carry warm water away from Equator
• Tropical organisms found at higher latitudes on
  west side of ocean
• Cold-favoring organisms live closest to equator
  on eastern side of oceans